Academic literature on the topic 'Circular formwork'

One of the applications of fiber-reinforced polymers in bridge construction is stay-in-place formwork. Fiber-reinforced polymer stay-in-place formwork, in the form of preformed tubes, provides easy form assembly, protection of steel reinforcement and concrete against corrosion and chemical attacks while also improving the strength and ductility of structural elements in earthquake resistant construction. Experimental research was conducted to investigate the seismic performance of fiber-reinforced polymer stay-in-place formwork for bridge columns. Tests of large-scale specimens were conducted under simulated seismic loading. The experimental program included circular and square columns confined with carbon fiber–reinforced polymer tubes. The results indicate that the use of carbon fiber–reinforced polymer tubes increases column inelastic deformability significantly. Bridge columns under low levels of axial compression exhibit inelastic drift capacities in excess of 4% before failing in flexural tension due to the rupturing of longitudinal reinforcement. These observations and experimental results were used to develop a displacement-based design procedure for concrete confinement for fiber-reinforced polymer–encased concrete columns. This article presents an overview of the experimental program and the design approach developed.

This paper summarizes research and development of an ice shell construction carried out in inland Hokkaido of Japan from 1980 to 2012.The ice shell is made of thin-walled curved ice plate and constructed according to the following method. (1) Building up a three-dimensional formwork by inflating a two-dimensional membrane bag covered with ropes anchored to the snow-ice foundation ring. (2) Covering the formwork with a thin saturated snow layer of less than 1 cm thickness by blowing milled snow with a rotary snow blower and spraying water with an adjustable nozzle, and letting it freeze naturally at temperatures below −10°C. (3) Repeating (2) until shell thickness reaches to the design thickness, then removing the bag and ropes for reuse. A number of ice shells were constructed as temporary winter structures while improving the construction technique through the repeated construction experiences. Based on the field experiments of 10–30 m ice domes (“ Xm ice dome” means the ice dome constructed by using Xm diameter of circular membrane bag in the formwork before inflation) which measured the deflection and temperature under long term period after the completion and further observed the behavior of the collapse, it was recognized that understanding the creep behavior is extremely important for evaluating the structural safety of the ice shell.

Recent advancements in the fields of fiber reinforced polymers (FRPs) have resulted in the development of new materials with great potential for applications in civil engineering structures, and due to extensive research over recent years, FRPs are now being considered for the design of new structures. This study describes how carbon fiber reinforced polymer jackets can be used to reinforce circular concrete columns. Fibers aligned in the circumferential direction provide axial and shear strength to the concrete, while fibers aligned in the longitudinal direction provide flexural reinforcement. Prefabricated FRP jackets or tubes would also provide the formwork for the columns, resulting in a decrease in labor and materials required for construction. Also, the enhanced behavior of FRP jacketed concrete columns could allow the use of smaller sections than would be required for conventionally reinforced concrete columns. Furthermore, FRP jacket reinforced concrete columns would be more durable than conventionally reinforced concrete columns and therefore would require less maintenance and have longer service life.Key words: bridge, carbon, column, concrete, confinement, fiber reinforced polymer, jacket, retrofitting, seismic, strengthening.

A reduced carbon footprint and longer service life of structures are major aspects of circular economy with respect to civil engineering. The aim of the research was to evaluate the interfacial bond properties between a deteriorated normal strength concrete structure and a thin overlay made of Eco-UHPC containing 50 wt% of limestone filler. Two types of formwork were used: untreated rough plywood and surface treated shuttering plywood. The normal strength concrete elements were surface scaled using water jets to obtain some degradation prior to casting of the UHPC overlay. Ultrasonic pulse velocity (UPV), bond test (pull-off test), and Scanning Electron Microscopy (SEM) combined with Energy Dispersive Spectrometry (EDS) were used for analysis. Elements repaired with the Eco-UHPC showed significantly improved mechanical properties compared to the non-deteriorated NSC sample which was used as a reference. The bond strength varied between 2 and 2.7 MPa regardless of the used formwork. The interfacial transition zone was very narrow with only slightly increased porosity. The untreated plywood, having a rough and water-absorbing surface, created a surface friction-based restraint which limited microcracking due to autogenous shrinkage. Shuttering plywood with a smooth surface enabled the development of higher tensile stress on the UHPC surface, which led to a more intensive autogenous shrinkage cracking. None of the formed microcracks penetrated through the entire thickness of the overlay and some were partly self-healed when a simple water treatment was applied. The project results showed that application of UHPC as repair material for concrete structures could elongate the lifespan and thus enhance the sustainability.

Over the last hundred years, shaft spillways have become widely used in hydraulic engineering practice due to their undeniable advantages: high discharge capacity, maximal water consumption per one cubic meter of concrete, point structure compactness. The modern theory of hydraulic calculations was formed based on works on the study of the operation of a circular spillway with a sharp edge carried out by Wagner in 1954. Although numerous hydraulic studies have not proved many of the statements Wagner's calculation methodology was based on, the materials of his studies have been presented in special hydraulic literature for hydraulic calculations up to date. The accepted design conditions of the drainage surface of the spillway shaft, which is round-cylindrical in the cross-section and in the form of a convex parabolic line in the longitudinal section, do not correspond to the possibilities of work. As a result, the drainage surface is replaced by a system of truncated cones, the joints of which cause flow separation from the drainage surface and the formation of vacuum zones. It results in approximate hydraulic calculations. To eliminate these disadvantages of hydraulic calculations and bring design developments in line with technological possibilities of works, it is possible to replace a round-cylindrical cross-section of the inner surface of the shaft with a polygonal one. In this case, the drainage surface will consist of a system of longitudinal wedges with one-dimensional curvature, for which the formwork can be made of flat sheets. This paper presents materials on the calculation and design of a shaft spillway of a hydroelectric complex with a dodecagonal cross-section for Algeria, and four shafts with an octagonal cross-section and two shafts with a tetragonal cross-section for Syria. The receiving hopper head is round-cylindrical, and the drainage surface is elliptical, which allows adapting the drainage surface to any initial design parameters of shaft spillways.

Abstract This paper proposes a new design for the shaft spillway of the Djedra dam (East Algeria). The procedure consists of replacing the circular section with a polygonal configuration of twelve (12) sections. The study of the model was divided into 5 different versions according to the variants of technical modifications of the water intake funnel; this configuration was tested on a hydraulic model in the laboratory of hydroelectric power plants of the Moscow State University of Environmental Engineering. The use of the polygonal section weir can greatly simplify the formwork of the structure, also the free entry funnel increases the discharge coefficient by 20%, without exposing the head of the weir to the risk of cavitation. In the event of submersion, the adopted design can ensure the crossing of an estimated relative flow with a probability of P = 0.01%, which means reducing the height of the dam by 0.68 m, and thus making the hydraulic structure more efficient economically and more reliable. The experimental model was produced on a 1:60 scale of the prototype, which guarantees self-simulation of the hydraulic phenomena of the Djedra dam, and its final design is judged to be hydraulically satisfactory and recommended for construction.